The torrent of words your baby has been hearing since birth is beginning to work its magic, although his understanding of words far outpaces his ability to use them. His babbling has turned to jabber and is probably starting to sound more like real words, phrases, and sentences. Your baby thinks he's saying something, so respond as if he really is!
Your baby still comprehends more from your tone than from your actual words, though. He can understand when he's pleased you, so offer specific praise, such as "You did a great job picking up the rattle." The more you talk to your baby — while preparing dinner, driving, or getting dressed — the more he learns about communication.
Your baby's starting to understand the word "no," though he may not obey it just yet. For example, you can expect him to try to touch something even after you've said not to. It's best to use the word "no" sparingly, and when you do use it, follow it by removing him from the scene of the crime and introducing him to a new activity.